1. Field of the Invention
This invention relates to an apparatus for inspecting automatic lock sliders incorporated in slide fasteners and used therein for opening and closing them, and more particularly to an apparatus for automatically inspecting the assembled sliders to determine infallibly by a simple mechanism whether or not the sliders are capable of fulfilling a prescribed automatic locking function.
2. Description of the Prior Art
The automatic lock slider for a slide fastener is provided with an engaging claw which is thrust elastically into a fastener chain guide channel inside a slider body by a spring set in the upper plate of the slider body. When a pair of long and narrow slide fastener chains having interlocking elements or fastener elements attached as regularly spaced to the lateral edges thereof are held in the guide channel inside the slider body and the engaging claw is thrust into the guide channel and then inserted in the gap between adjacent elements by the force of the spring, the slider is brought into engagement with the slide fastener chains by the engaging claw and is no longer allowed to slide. When the engaging claw is lifted up in spite of the force of the spring and extracted from the gap between the adjacent elements by the use of a pull tab, the slider is released from the engagement with the slide fastener chains and consequently allowed to slide on the slide fastener chains and open or close the slide fastener. In order for the slider to lock and unlock the slide fastener chains smoothly in consequence of the use of the pull tab, therefore, the spring for urging the engaging claw must be possessed of prescribed spring force.
The slider mentioned above is generally assembled as a finished product by sequentially setting a plurality of parts such as the pull tab, the spring, and the cover in place in the slider body. Owing to possible variations in the qualities of these parts and in the conditions of assembly works, the assembled sliders have inevitably included defective products.
The apparatus disclosed in GB 2184540B has been known as inspection means intended for efficiently detecting and eliminating these defective products at the final stage of the process of production. This inspection apparatus comprises a table for horizontally supporting and intermittently moving sliders, a vertically movable disk or elevating disk disposed above the table and vertically reciprocated at a predetermined stroke while the table is at a stop, a retainer rod for retaining a slider body in a peripheral recess of the table and a pressure rod for pressing a pull tab of the slider, severally mounted vertically movably on a support block fixed to the elevating disk as elastically urged downwardly, a sensor lever pivotally supported on the lower part of the retainer rod and extended in a substantially horizontal direction, the sensor lever having a sensing projection extended downwardly from the middle portion thereof so as to collide against the pull tab of the slider, a detecting unit possessing a pair of upper and lower non-contact type detectors disposed within the range in which the free end of the sensor lever produces a vertical motion, and an electric-signal discrimination circuit connected to the detecting unit.
This inspecting apparatus accomplishes detection of a defective slider on the principle that the condition of contact of the sensing projection with the pull tab of the slider held on the table and the vertical motion of the free end of the sensor lever due to the pressure exerted by the pressure rod are different between a non-defective slider and a defective slider, this difference induces a difference in the signal from the detecting unit, and the electric-signal discrimination circuit, on receiving the signal, discerns the presence or absence of a defect in the slider under inspection. Then, the electric-signal discrimination circuit controls the operation of means for discharging sliders from the table in accordance with the result of discernment between the non-defective and defective conditions.
Incidentally, in the apparatus for automatic assembly of sliders, the table and the elevating disk mentioned above are synchronously operated and the apparatus, therefore, is allowed to perform a series of works ranging from assembly through inspection. To be specific, the table is divided into several sections such as a slider body supply section, a pull tab fitting section, a spring fitting section, a spring fixing section, a cover fitting section, and a inspection section, the elevating disk is provided in the areas or vicinities thereof corresponding to the sections mentioned above with machining devices suitable for the works to be performed in the sections, and the slider bodies held on the table are moved intermittently by the table and subjected sequentially to the works.
For the purpose of expediting the component works of the process ranging from assembly to inspection of sliders and improving the productivity of the process, therefore, it is necessary that the speed of the intermittent motion of the table should be increased and the speed of the vertical motion of the elevating disk or board should be proportionately increased. As a result, the overall speed of the process will be heightened.
When the inspecting apparatus of the conventional technique mentioned above is used for the process of inspection, however, since the support block which holds the retainer rod and the pressure rod is directly fixed to the elevating board, an increase in the speed of vertical reciprocation of the elevating board inevitably adds to the speed of vertical reciprocation of the support block and that of the retainer rod and the pressure rod supported thereon as well. As a result, the sensor lever which is pivotally supported at one point by the retainer rod fails to follow the speed of vertical reciprocation and collides at a relatively high speed against the pull tab of the slider. The repulsive force arising from this collision causes the sensor lever to jump and entails the problem that the apparatus will provide no precise inspection as by committing the error of rating a non-defective slider as a defective slider.